Appendix II, #33 the Babcock-Wilcox, and the Herrtsdwf is a coil boiler with f>ump circulation. (Saff. 918, 993,0;^ 1061.) Plugs (see also p. 755). Fig. 802 is a section of one of these as introduced by the National Boiler Insurance Company. The white-metal should be renewed annually. CHAPTER YIIL JP. 367. Modulus of Resilience,— -The greatest clastic stress is often called jtrocf stress. Then, from diagram 2, Fig, 326, we may define resilience as ( half proof load x proof strain,' or Resilience But A -. Resilience and W (A volume). The quantity /2~E is termed the modulus oj resiliency and measures resistance to impact per cubic inch of the bar. 61 .—Compare the resilience per unit volume of two bolts A arid B, In which for ^ Its length A has a sectional area *8 of the remaining ft : and B has for & its length a sectional area 'B of the remaining $j (Hons. Mach. Canst. Exam. i8«9i). In each case let/"« unit stress on smaller area and 'Sj « nnlt stress on larger area. Also let a « larger area, an<l *S a » smaller area, Then, talcing "bolt A, total resilience V.'